The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1A, a transmitter 100 of a wireless device is shown for example only. The transmitter 100 includes a baseband processing module 102, an upconverter module 104, a power amplifier module 106, and an antenna 108. While a single antenna is shown, the transmitter 100 may include multiple antennas. For example only, the multiple antennas may be arranged in a multiple-input multiple-output (MIMO) configuration. The baseband processing module 102 generates baseband signals that include data to be transmitted by the transmitter 100. The upconverter module 104 upconverts the baseband signals to radio frequency (RF) signals. The power amplifier module 106 amplifies the RF signals and transmits the amplified RF signals via the antenna 108.
Referring now to FIG. 1B, an example of the transmitter 100 is shown. The baseband processing module 102 outputs an in-phase (I) signal and a quadrature phase (Q) signal that include the data to be transmitted by the transmitter 100. The upconverter module 104 includes low-pass filter (LPF) modules 110 and 112 to remove high-frequency noise in the I and Q channels, respectively. The filtered I and Q signals are input to mixers 114 and 116. The mixers 114, 116 may be called I-channel and Q-channel mixers (or I and Q mixers), respectively.
The I and Q mixers 114, 116 upconvert the I and Q signals from baseband frequency to radio frequency (RF). The I and Q mixers 114, 116 are driven by clock signals having a predetermined reference frequency. The clock signals are generated by a local oscillator (OSC) 118, a frequency divider (DIV) 120, and a −90° phase shifter 121. A summer 122 combines upconverted RF outputs of the I and Q mixers 114, 116 into a signal that is input to the power amplifier module 106. The power amplifier module 106 amplifies the signal and drives the antenna 108, which transmits the signal.